An estimated 150 million UTIs occur annually on a global basis, accounting for direct health care costs exceeding 6 billion dollars and making UTIs a very significant public health burden. This program project proposes studies that will improve our understanding of the epidemiology, microbial ecology, molecular pathogenesis and prevention of UTIs. The objectives of the project will be met through the development of a multidisciplinary research team that will collaborate to carry out four interrelated projects. Project 1 will undertake a double-blind placebo-controlled trial to determine whether a Lactobacillus crispatis vaginal probiotic will reduce the incidence of recurrent UTIs in women. The trial will also study adherence of the probiotic strain to vaginal epithelial cells from the subjects and will thus provide insight into the host and microbial mechanisms involved. Project 2 will address the hypothesis that cell surface glycosphingolipids in the bladder and vaginal epithelium are structurally organized into pleotrophic plasma membrane assemblies called caveolae and that caveolae participate in the initial epithelial response to attachment and uptake of uropathogenic e. coil Project 3 will employ two novel technologies that were developed during the previous funding period, namely high density microarrays and whole genome mutation scanning to characterize on a genomic level the molecular adaptation that uropathogenic E. coil strains undergo in the course of recurrent UTIs and in shifting from an asymptomatic to symptomatic infection. The project will also define how such adaptive evolution affects the ability of uropathogens to bind and invade epithelial cells, induce inflammation and resist phagocytosis. In Project 4, the association of host susceptibility to recurrent cystitis or pyelonephritis with known or novel mutations in specifically selected candidate host genes will be examined. The candidate genes to be studied are toll-like receptors (TLR2, TLR4, and TLR6), chemokine receptors (CXCRI and CXCR2), and interferon y receptors (IFN-yR1 and IFN-yR2). A laboratory core will provide microbiological studies, primary bladder and vaginal epithelial cells, characterization of urovirulence genes, bacterial adherence assays and other resources to the projects. An Administrative/Biostatistical Core will coordinate the overall project and provide biostatistical expertise to all investigators. The proposed studies will result in an improved understanding of pathogenetic mechanisms in UTIs and will result in new approaches to prevention of UTIs.